1. Field of the Invention
The present invention relates to a keypad structure, and more particular to a method of manufacturing a light guide plate.
2. Description of Prior Art
A keypad structure is one of the main input peripherals of an electronic device, and each keypad on the keypad structure generally has a corresponding numeral, text, phonetic symbol, radical of an input method and different functional figures, so that an user can input data, or execute various functions of the electronic device. Therefore, a keypad structure is an important input peripheral for an electronic device.
Since an electronic device is usually operated in an environment with sufficient light, therefore users can see the position of each keypad clearly and will not press a wrong keypad. If the electronic device is operated in a dark environment, users will have difficulties of operating the keypads on the electronic device. Therefore, internal layers of the keypad structure usually include a backlight source, and the light produced by the backlight source allows users to see the position of each keypad clearly in a dark environment, and prevents a user from pressing a wrong keypad.
In general, the backlight source used in a traditional keypad structure is comprised of a light guide plate and a light emitting diode. When an electronic device is turned on, the light emitting diode is lit, and the light is guided into the front end of the light guide plate, and then projected from the light guide plate to the bottom of each keypad to display a hollow numeral or figure at the surface of the keypad, so as to prevent users from pressing a wrong keypad when operating the keypad in a dark environment. However, when the light of the light emitting diode is guided from the front end to the rear end of the light guide plate, the brightness of the light becomes increasingly weak, and thus the brightness for showing the numeral and figure at the surface of the keypad with respect to the rear end of the light guide plate is insufficient.
In recent years, manufacturers add light-guiding micro structures to the light guide plate to solve the problem of the unevenly distributed light, such that when the light is guided into the light guide plate, the light-guiding micro structures can change the light path, and focus the refraction of light onto each keypad. Since a traditional light guide plate having light-guiding micro structures is produced by an ink jet technology, resins injected by an ink jet head is formed directly on a carrier to produce light-guiding micro structures, but the ink jet head must be moved back and forth along the y-axis to spray the resins onto the carrier, and thus the production efficiency becomes very low.
Another manufacturing method is an imprint method that uses a roller for a rolling process, and the surface of the roller has a plurality of protruding light-guiding micro structures, such that if the roller is rolled on a surface or a backside of the soft and firm carrier, the carrier will be deformed, and the carrier will be bounced back towards a same direction. Therefore, it is necessary to adjust the pressing force of the roller according to the bouncing force produced after the material of the carrier is deformed, if the roller is used for the rolling. If the pressing force of the roller is not adjusted precisely, then defects of the light-guiding micro structure will result, and the light cannot be focused and refracted onto the keypad.